Local conditioning induction-type apparatus employing primary inlet air as a power means for controlling temperature

ABSTRACT

In a conditioning apparatus unit to be used in relation with conditioning systems of the type having four pipes for the secondary water, wherein the temperature is controlled by varying the secondary air flow passing through two heat-exchangers and a by-pass section by means of valve assemblies, the valve assemblies are actuated by the primary air feeding the same apparatus at a pressure value comprised in the range between 15 and 100 Kg/m2. Each valve assembly relating to a heat-exchanger is operated by an expansion lung fed by the inlet primary air through a valve controlled by a thermostatic device. A linkage mechanically connects the valve assembly of the by-pass section with the valve assemblies of the heat-exchangers in such a manner that when one of the valve assemblies relating to the heatexchanger is at least partially open, the other valve assembly is locked in the &#39;&#39;&#39;&#39;close&#39;&#39;&#39;&#39; position and only the by-pass valve assembly can be operated by the said one valve assembly. At each position of either of the two heat-exchangers valve assemblies a given position of the by-pass valve assembly is associated and in particular to the &#39;&#39;&#39;&#39;open&#39;&#39;&#39;&#39; position of one of them the by-pass valve is closed.

United States Patent [1 1 Serratto Oct. 15, 1974 [76] Inventor: AngeloSerratto, C. S. lndipendenza,

5, Milan, Italy 22 Filed: Feb. 27, 1973 211 Appl. No.: 336,181

[30] Foreign Application Priority Data Mar. 1, 1972 Italy 21255/72 [52]US. Cl 165/123, 165/16, 165/37, 236/87 [51] Int. Cl F24f 3/04, F28f13/12 [58] Field of Search 165/123, 16, 37, 122; 236/87, 1 B

[56] References Cited UNITED STATES PATENTS 2,109,650 3/1938 Rather236/1 B 3,120,344 2/1964 Wood 165/123 3,172,463 3/1965 Bowman.. 165/1233,208,508 8/1965 Bryans 165/123 3,213,928 10/1965 Anderson 165/1233,452,811 7/1969 Yerdon 165/123 3,470,945 10/1969 Schmidt"; 165/1233,512,578 5/1970 Honmann 165/122 3,623,542 11/1971 Fragnito 165/1233,730,430 5/1973 Osheroff 236/87 3,744,556 7/1973 Church 165/123 PrimaryExaminer-Manuel A. Antonakas Assistant Examiner-Daniel J. OConnorAttorney, Agent, or FirmRose & Edell [57] ABSTRACT In a conditioningapparatus unit to be used in relation with conditioning systems of thetype having four pipes for the secondary water, wherein the temperatureis controlled by varying the secondary air flow passing through twoheat-exchangers and a by-pass section by means of valve assemblies, thevalve assemblies are actuated by the primary air feeding the sameapparatus at a pressure value comprised in the range between 15 and 100Kg/m' Each valve assembly relating to a heat-exchanger is operated by anexpansion lung fed by the inlet primary air through a valve controlledby a thermostatic device. A linkage mechanically connects the valveassembly of the by-pass section with the valve assemblies of theheat-exchangers in such a manner that when one of the valve assembliesrelating to the heat-exchanger is at least partially open, the othervalve assembly is locked in the close position and only the by-passvalve assembly can be operated by the said one valve assembly. At eachposition of either of the two heat-exchangers valve assemblies a givenposition of the by-pass valve assembly is associated and in particularto the open position of one of them the by-pass valve is closed.

9 Claims, 10 Drawing Figures PATENTEDUBI 15 m4- 3.841.398 SHEET 30F 4LOCAL CONDITIONING INDUCTION-TYPE APPARATUS EMPLOYING PRIMARY INLET AIRAS A POWER MEANS FOR CONTROLLING TEMPERATURE BACKGROUND OF THE INVENTIONThis invention relates to a local conditioning induction-type apparatusemploying primary inlet air as a power means for controllingtemperature. In particular the present invention relates to a localconditioning induction-type apparatus for conditioning systems with fourpipes of the secondary water and wherein the temperature is controlledby varying the secondary air flow passing through the heat-exchangersand a py-pass section, having valve assemblies for varying said air flowwhich are actuated by the same primary inlet air, at the usual feedingpressure of such air.

It is known that the induction-type conditioning apparatus for systemswith four pipes of the secondary water essentially comprise a plenumchamber (possibly provided with a silencer) where primary air is fed ata pressure usually in a range of values from 15 to I Kg/m a row ofnozzles wherein this pressure is converted into kinetic energy and thenvelocity; two water- /air heat-exchangers, one fed by cooled water andthe other by hot water; a by-pass section; valve assemblies for guidingthe secondary air sucked from the room into a chamber which is placeddownstream of the nozzles exclusively through either of theheat-exchangers, or the by-pass section only, the whole beingconstructed and connected so as to form a single unit.

It is also known that such conditioning apparatus use, for controllingthe valve assemblies guiding the secondary air flow, actuators which maybe pneumatic, electromagnetic or electronic. When pneumatic actuatorsare used, one or morecompressors compress air at a pressure of70,00080,000 Kg/m within suitable reservoirs from which compressed air,upon filtering, drying and pressure releasing to about I 1,000 Kg/m isfed to all the control devices, in this specific case thermostats, bymeans of copper, steel or plastic material tubes. Air outflows from eachthermostat at a pressure variable in a range from 0 to 1,100 Kg/m andthe value of the varying pressure is a function of the temperaturesensed by the thermostat, which in turn is connected with one or moreactuators through other tubes, usually of copper or plastics. Acompression station is therefore necessary and also a distributionsystem for the compressed air, with rather high costs of installationand operation.

Electric or electronic actuators are seldom used, due to their highprime cost and delicacy: on the other hand also in this case an electricfeed line and connections between thermostats and actuators arerequired.

SUMMARY OF THE INVENTION Therefore it is an object of the presentinvention to provide a conditioning apparatus which overcomes theabove-mentioned inconveniences of the control devices of pneumatic,electric and electronic type previously described, said conditioningapparatus having a control device of the pneumatic type, but employingas motor fluid the same primary air fed into the plenum chambers of theinduction apparatus, at the relatively low pressure usually employed,that is comprised in a range of values from about to about 100 Kg/m Withsuch a low pressure of the motor fluid when compared with the pressurein a conventional automatic control device, it is not possible the useof the common thermostats and actuators. Therefore it is another objectof the present invention to provide control devices capable of operatingat pressure values as usually employed in feeding primary air to theinduction apparatus.

The induction-type conditioning apparatus according to the invention,comprising valve assemblies for varying the secondary air flow throughthe heat-exchangers and the by-pass section, is characterized by thefact that each valve assembly associated with a heat exchanger isactuated by an expansion lung fed by the inlet primary air through avalve controlled by a thermostatic device, there being provided meansadapted to connect the valve assembly of the by-pass section with thevalve assemblies of the heat-exchangers and interlocking means forpreventing secondary air from passing contemporarily through the twoheatexchangers.

The main advantage of the conditioning apparatus of the invention isgiven by the fact that, in comparison with the prior art apparatus, anair compression station and a distribution line of the compressed airare no more necessary for the temperature control device in the case ofpneumatic control. On the other hand there is neither necessity ofelectric or electronic actuators and relative conductors for theconnection with the thermostat in case of this type of control, thushighly reducing the cost of the apparatus itself.

BRIEF DESCRIPTION OF THE DRAWINGS The conditioning apparatus of theinvention will be now fully described with reference to a preferredembodiment thereof, given by way of example, with the aid of the annexeddrawings, in which:

FIG. 1 is a cross-sectional view of an embodiment of the conditioningapparatus according to the invention;

FIGS. 2a, 2b, 2c are cross-sectional views, respectively along linesA-A, B-B, CC of a thermostat of the conditioning apparatus of FIG. 1;

FIG. 3 is a diagrammatic side view of the apparatus, showing inparticular the linkage interconnecting the valve assemblies of theheat-exchangers and of the bypass section; and

FIGS. 4a to 4e show some details of the linkage of FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to FIG.I, a local conditioning induction-type apparatus for a four-pipesconditioning system having a temperature control by means of variationof the secondary air flow passing through two heatexchangers and aby-pass section comprises a plenum chamber 1 of the primary air possiblyprovided with deadening panels 2, 3 and air-jet nozzles 4. In thesenozzles the potential energy of the primary air (static pressure) isconverted into kinetic energy in the chamber 5 downstream of thenozzles, where a low pressure zone is created. The rear panel forclosing the apparatus is indicated by 6 and '7 is the top outlet of themixture of primary and secondary air, sucked through one of theheat-exchangers 8, 11 and/or the by-pass section 10 by means of thedepression within chamber 5. The

upper heat-exchanger 8 will be preferably that for cooling the secondaryair and is provided with a water trap 9, while the heat-exchanger 11 ispreferably for heating the secondary air. There is also provided aninner baffle 12 for improving the induction properties of the apparatus.

The valve assembly for controlling the inlet of secondary air throughthe heat-exchanger 8 has reference number 13, and 14 is thecorresponding expansion lung having a protective bellows 15, while 16 isthe reference number of at least one return spring of the valve assembly13. Similarly 17 is the valve assembly for controlling the inlet ofsecondary air passing through the heat-exchanger 11, provided with anactuating lung 18 and corresponding protective bellows 19, as well asone or more return springs 20.

The by-pass section 10, through which passes the secondary air withoutbeing treated, is also provided with a valve assembly 21 rotatablymounted on a pivot 24; similarly the valve assembly 13 is mounted on apivot 22 and the valve assembly 17 on a pivot 23. Air-tight seal gasketshave been referred to by 25.

It is obvious that the so far described structure of the conditioningapparatus, substantially known except for the valve assemblies actuatinglungs and their auxiliary equipment, is not the object of the presentinvention and may be varied by employing different embodiments or otherarrangements of the parts forming the apparatus itself. For example inanother possible embodiment the by-pass section could be eliminated aswill be explained later on.

According to the present invention each expansion lung 14, 18communicates with one of the three ports of a thermostat shown in FIGS.2a, 2b, 20. This thermostat substantially comprises a casing 34, a cover35, a temperature responsive element such as a bimetallic spiral 36 withcalibration device 37, a seal bellows 38 of plastic material and twopneumatic valves 39, 40. Each valve 39, 40 comprises respectively aribbed slide guide 41, 42, a shutter 43, 44 and a return spring 45, 46for elastically taking up the further stroke of the thermostatic elementwhen the shutter is closed. The two shutters 43, 44 slide within the tworibbed guides 41, 42 along and pin 47 an are actuated by a control yoke48 rigidly connected to the bimetallic spiral 36. The valve 39communicates with a port 50 having laterally a the aperture 52, while toth valve 40 corresponds a port 51 having a lateral vent aperture 53.There is also provided a port 49, common to the both valves, which isconnected through a tube of rubber or plastics with the plenum chamber 1of primary air through a fitting54 (FIG. 1). Port 50 is insteadconnected with the lung 14 of the heat-exchanger 8 through a fitting 56(FIG; 1) and port 51 with lung 18 of the heatexchanger 11 through afitting 55 (FIG. 1).

At rest, both the pneumatic valves 39, 40 are open in the positionrepresented at FIG. 2a, thereby the primary air from the port 49 feedsat the same time both the lungs 14, 18 which thus maintain the valveassemblies 13, 17 in a closed position. Therefore the secondary air isprevented from passing through the heatexchangers 8, 11 while the bypassvalve assembly 21 is in the position c"'--c"' shown by phantom lines atFIG. 1. At this stage the air flow from the two ports 52, 53 is lowerthan that entering the two valves.

The bypass valve assembly 21 is connected with the valve assemblies 13,17 by means of a linkage an embodiment of which is shown by way ofexample at FIGS. 3 and 4. This linkage has the function of allowing theby-pass valve assembly 21 to be actuated either by the valve assembly 13alone or by the valve assembly 17 alone, at the same time locking theother valve assembly until the one which is in movement reaches its stopposition, corresponding to the complete interruption of the passage ofsecondary air through the relative heat-exchanger.

With reference to FIG. 3, there is shown a side view of the apparatus,namely of the left side from the point of view of the heat-exchanger andby-pass section side. The pivots 22, 23 for the rotation of valveassemblies 13, 17 are provided with two cranks 26, 27 which are fixedlyconnected, through two rods 28, 29 of adjustable length, with two racks30, 31. The racks, by engagement with a sector gear 32, fixedly mountedon the pivot 24 for the rotation of the by-pass valve assembly, causethe latter to rotate. The spring 33 has the function of maintaning at arest position the by-pass valve assembly 21, which positioncorresponding to the complete open position C"'c"' (see FIG. 1).

With reference to FIGS. 4a-4e, the interlocking device between valveassemblies 13, 17 is shown more in detail. On the same pivot 24 of thesector gear 32 two levers 57, 57' are keyed, which are identical andsymmetric with respect to the pivot itself, each of them being formedwith a pawl 58, 58 and a projecting part or bracket 59, 59. Each lever,which is illustrated in detail in a side view at FIG. 40 and incross-section along line D-D at FIG. 4d, under the action of a spring60, 60 respectively is kept in such a position whereby the bracket 59,59' engages with the end portion of the rack 31, 30 respectively, thuspreventing any movement thereof. Only when pawl 58, 58 is engaged by thetooth 61, 61 respectively of the rack 30, 31 the lever 57, 57 overcomesthe action of the spring 60, 60' respectively of the rack 30, 31 thelever 57, 57' overcomes the action of the spring 60, 60' respectivelyand rotates around its axes disengaging the bracket member 59, 59 fromthe end of the rack 31, 30 respectively. One of he racks 31, 30 is soallowed to slide and therefore the valve assembly 17, 13 to which thelever 57, 57' is linked through the rods 28, 29 and the cranks 27, 26,is caused to rotate.

At the above described rest position, both the cranks 26, 27 are inposition a-a and b-b (FIGS. 4a, 4b), corresponding to both the valveassemblies closed, and the pawls of the two levers are both engaged bythe teeth of the racks, which therefore are allowed to slide.

It is to be noted that 62, 62 are referred to the supports ofrespectively springs 60, 60', rigidly fixed to the side 66 of theapparatus. Two rollers 64, 65, mounted on a shaft 63 ensure the contactbetween sector gear 32 and racks 30, 31 respectively.

Starting from the above described rest situation and supposing that thethermostat detects a decrease of temperature in comparison with that ofreference and also supposing that heat exchanger 8 is the cooling onewhile heat-exchanger 11 is the heating one, the bimetallic element 36biases the yoke 48 so that the latter, by compressing the spring 46,moves the shutter 44 to the right-hand gradually closing the inlet ofprimary air to the port 51, until shutter 44 engages the head of theright end of pin 47. At the same time the shutter 43 is also moved tothe right-hand completely opening the port 50. A portion of the airwithin lung 18 of the heatexchanger 11 (high temperature), throughfitting 55 and a tube for the connection with port 51 (not represented),discharges through vent aperture 53. Therefore the pressure in the lung18 decreases and the valve assembly 17 of the heat-exchanger 11, underthe action of return spring 20 gradually opens the passage of secondaryair through the same heat-exchanger (high temperature). The rotation ofthe valve assembly 17 towards the open position causes thecounterclockwise rotation of the crank 27, the downwards movement of therod 29 and the rack 31 connected therewith, the clockwise rotation ofthe sector gear 32 and therefore of the by-pass valve assembly 21. Assoon as the rack 3l starts with the downward movement, the tooth 61'stops engaging the pawl 58 of the lever 57' thus allowing the bracketmember 59 to lock the rack 30, linked to the valve assembly 13 of theheat-exchanger 8 (low temperature) through the rod 28 and the crank 26.

Thus, while at rest both the racks can slide and therefore both thevalve assemblies can open, as soon as one of them moves from the closedposition, this immediately prevents any movement of the other. This isprovided in spite of the impossibility that during the usual operationboth the valves will be contemporarily caused to close, as explainedhereabove, but in view of avoiding that the opening of both the valveassemblies occurs due to incidental rude movements, eg a manual knock.In full heating stage, port 51 is completely closed, lung 18 at theatmospheric pressure, valve assembly 17 at the position b'-b' of FIG. 1,that is completely open, corresponding to the position b'b' of the crank27 FIG. 4b), by-pass valve 21 at the position cc", that is completelyclosed, and valve assembly 13 at the position 0-0 of FIG. 1, that iscompletely obstructing the passage of air through the lowtemperaturebeat-exchanger.

Of course the opposite occurs if the thermostat, with respect to thereference value, detects an increase of temperature until reaching thefull cooling stage wherein valve assembly 13 is in a position ofcomplete opening a'-a, by-pass valve assembly 21 closed at cc' and valveassembly 17 completely closed at the position b-b.

The three valve assemblies can obviously have all the intermediatepositions from the full heating stage to the full cooling stage, becausethe position of the two pneumatic valves of the thermostat, the airpassing therethrough and flowing from the two ports 52, 53 give rise tovariable pressure conditions within the two lungs with the consequencethat the valve assemblies can cover all the intermediate positions withinterlocked movements, but in such a manner that while valve 13 movesfrom a'-a' to 0-0, by-pass valve moves from c"-c" to c"'-c"' andsubsequently while valves 17 moves from b-b to b'-b', by-pass valvesmoves from c"'c" to c'c'. The actuation of the valve assemblies by meansof the primary air at the relatively low pressure employed byinduction-type systems is possible due to the large contact surfacesexisting between lungs and valve assemblies, which are essentially givenby the whole surface of the valves themselves, to the fact that thevalve assemblies rotate on anti-friction bearings, and to the very lowdifference of pressure between the two surface of the control valveassemblies.

It is to be understood that the by-pass section is not absolutelynecessary and it may be eliminated, as stated above, as well as thevalve assemblies 21 and the linkage shown at FIGS. 3 and 4. In this casethe function 5 carried out by the by-pass section when the valvesassemblies 13, 17 are in such a position to shut off theheat-exchangers, occur at the outlet 7 because primary air flowing fromthe nozzles 4 has still as much kinetic energy as to cause room air tobe sucked. The kinetic energy of the primary air is substantially thesame throughout the apparatus unit, from the nozzle 4 to the outlet 7due to the fact that there is no passage of air through the twoheat-exchangers, closed by the valve assemblies.

It is further to be appreciated that the induction apparatus of thepresent invention may be shipped from the production to the installationplace with the plenum chamber and expansion lungs, thus reducing furtherinstallation time and costs. Furthermore only one thermostat can controla plurality of conditioning apparatus which causes the setting up coststo be sunstantially reduced.

Additions and/or modifications may be made by those skilled in the artto the above described and illustrated embodiment of the induction-typelocal conditioning apparatus of the present invention without departingfrom the scope and spirit thereof. In particular it will be possible tomodify the arrangement and number of the elements forming the apparatussuch as plenum chamber, heat-exchangers, controlling valves and by-passsection, the last being possibly missing, as previously stated.

What I claim is:

I. An induction-type air conditioning system of the type employing firstheat exchanger means for cooling air, second heat exchanger means forheating air and a respective pair of pipes for each heat exchanger meansto conduct temperature-treated fluid to and from said heat exchangermeans, said system comprising:

a housing;

a source of primary air including: plenum means located in said housingfor conducting said primary air, and nozzle means for issuing a primaryair stream from said plenum means;

means defining an air flow passage in said housing, said air flowpassage being positioned to receive the primary air stream from saidnozzle means and to direct said primary air stream externally of saidhousing;

means defining an aspiration opening into said air flow passage, saidaspiration opening being oriented to permit secondary air to beaspirated therethrough by said primary air stream flowing in said airflow passage;

means defining first, second and third air inlets into said housing,said first heat exchanger means being positioned in the path of saidfirst air inlet to cool air entering said housing via said first airinlet, said second heat exchanger means being positioned in the path ofsaid second air inlet to heat air entering said housing via said secondair inlet, said third air inlet serving as a by-pass inlet to permitentry of untreated air into said housing;

first actuable damper means movable between extreme opened and closedpositions to proportion air inflow through said first air inlet andhaving a front surface configured to block air flow through said firstair inlet when said first damper means is in its closed position, saidfirst damper means also including a rear surface;

first bias means for continuously urging said first damper means towardsits opened position;

a first actuator compartment located in said housing and defined on atleast one side by the rear surface of said first damper means;

first inflatable and expansible actuator means disposed in said firstcompartment for urging said first damper means towards its openedposition to a degree determined by the degree of inflation of said firstactuator means;

second actuable damper means movable between extreme opened and closedpositions to proportion air inflow through said second air inlet andhaving a front surface configured to block air flow through said secondair inlet when said second damper means is in its closed position, saidsecond damper means also including a rear surface;

second bias means for continuously urging said second damper meanstowards its opened position;

a second actuator compartment located in said housing and defined on atleast one side by the rear surface of said second damper means;

second inflatable and expansible actuator means disposed in said secondcompartment for urging said second damper means towards its openedposition to a degree determined by the degree of inflation of saidsecond actuator means;

control means for controllably inflating and deflating said-first andsecond actuator means with primary air, said control means includingthermostatic valve means responsive to the temperature in an environmentbeing conditioned by said primary air stream for inflating one anddeflating the other of said first and second actuator means with primaryair;

third actuable damper means movable to two extreme closed positionsthrough an opened position to proportion air inflow through said thirdair inlet;

linkage means for connecting said first and second damper means to saidthird damper means such that said third damper means is in its openedposition and permits maximum air flow through said third air inlet whenboth of said first and second damper means are closed.

2. The system according to claim 1 wherein said thermostatic valve meansincludes first and second valves connected to receive primary airthrough a common feeding port, said valves having respective outletports connected in parallel and feeding said first and second inflatableactuators, respectively, said valves being arranged so that at least oneof said outlet ports is open at any time to feed said primary air toinflate its associated inflatable actuator and thereby close thecorresponding one of said first and second damper means, said systemfurther including bias means for maintaining said first and seconddamper means open when the associated inflatable actuator is deflated,whereby contemporaneous opening of both said first and second dampermeans is prevented.

3. The system according to claim 2 wherein said first and second valveseach includes a vent aperture for discharging primary air from theassociated inflatable actuator when said each valve is closed, therebycausing the associated one of said first and second damper means toopen.

4. The system according to claim 3 wherein said thermostatic valve meansis responsive to a predetermined reference temperature in theenvironment being conditioned for partially opening both said first andsecond valves, whereby said first and second actuators maintain saidfirst and second damper means closed, the rate of air discharge fromsaid vent apertures being less than the rate of primary air flow throughsaid common feeding port.

5. The system according to claim 1 wherein said thermostatic valve meansis responsive to the temperature in said conditioned environment beingless than a predetermined reference temperature for blocking primary airinflow to said second inflatable actuator, whereby secondary air flowsthrough said second heat exchanger means, and wherein said thermostaticvalve means is responsive to the temperature in said conditionedenvironment being greater than said predetermined reference temperaturefor blocking primary air inflow to said first inflatable actuatorwhereby secondary air flows through said first heat exchanger means.

6. The system according to claim 1 further comprising means for biasingsaid third actuable damper means in an open rest position, said thirdactuable damper means being rotatably mounted for rotation between twoclosed positions which are symmetrically disposed relative to said restposition.

7. A local conditioning induction-type apparatus for conditioningsystems with four pipes of secondary water, comprising:

first and second heat exchangers, each arranged to have said secondarywater flowed therethrough via a respective pair of said four pipes;

a by-pass flow section located between said first and second heatexchangers;

a primary air flow section through which primary air is directed toflow, and including an aspiration opening through which secondary airflow is aspirated by primary air flow;

first and second damper means for controlling the temperature of saidprimary air flow for controlling secondary air flow to said aspirationopening through said first and second heat exchangers, re-

, spectively;

third damper means for controlling the temperature of said primary airflow by controlling secondary air flow to said aspiration openingthrough said bypass flow section;

first and second expansion lung actuator means for alternatively openingand closing said first and second damper means, respectively;

thermostatically controlled valve means for conducting primary air toinflate said first and second expansion lung means in response totemperature conditions in an environment being conditioned by saidprimary air;

connecting means linking said first and second damper means to saidthird damper means for controlling the position of said third dampermeans in accordance with the positions of said first and second dampermeans; and

interlock means for preventing secondary air from passing contemporarilythrough said first and second heat exchangers;

wherein said third damper means is biased open at a rest position by areturn spring and is rotatably mounted on a pivot about which it isrotatable between two closed positions symmetrically disposed relativeto said rest position; and

wherein said connecting means comprises a sector gear rigidly mounted onsaid rotation pivot of said third damper means, which sector gear meshesat the same time with two racks, each rack being connected witth one ofsaid first and second damper means, said interlock means being providedfor preventing any one of said racks from moving when the other rack isoperated by the movement of the associated damper means.

8. An apparatus according to claim 7, wherein said interlock meanscomprises two identical and symmetric leverspivotedly mounted on thesame rotation pivot of said sector gear, each lever having a pawladapted to be engaged by one of said racks and a bracket means adaptedto engage an end of the other rack, both said levers being capable ofrotating against the action of contrasting spring means as said pawl ofone lever is engaged by a tooth of the associated rack, therebydisengaging said bracket means from the other rack.

9. An apparatus according to claim 7, wherein said racks are connectedwith said first and second damper means by means of rods havingadjustable length and cranks mounted on the rotation pivots of the samedamper means.

1. An induction-type air conditioning system of the type employing firstheat exchanger means for cooling air, second heat exchanger means forheating air and a respective pair of pipes for each heat exchanger meansto conduct temperature-treated fluid to and from said heat exchangermeans, said system comprising: a housing; a source of primary airincluding: plenum means located in said housing for conducting saidprimary air, and nozzle means for issuing a primary air stream from saidplenum means; means defining an air flow passage in said housing, saidair flow passage being positioned to receive the primary air stream fromsaid nozzle means and to direct said primary air stream externally ofsaid housing; means defining an aspiration opening into said air flowpassage, said aspiration opening being oriented to permit secondary airto be aspirated therethrough by said primary air stream flowing in saidair flow passage; means defining first, second and third air inlets intosaid housing, said first heat exchanger means being positioned in thepath of said first air inlet to cool air entering said housing via saidfirst air inlet, said second heat exchanger means being positioned inthe path of said second air inlet to heat air entering said housing viasaid second air inlet, said third air inlet serving as a by-pass inletto permit entry of untreated air into said housing; first actuabledamper means movable between extreme opened and closed positions toproportion air inflow through said first air inlet and having a frontsurface configured to block air flow through said first air inlet whensaid first damper means is in its closed position, said first dampermeans also including a rear surface; first bias means for continuouslyurging said first damper means towards its opened position; a firstactuator compartment located in said housing and defined on at least oneside by the rear surface of said first damper means; first inflatableand expansible actuator means disposed in said first compartment forurging said first damper means towards its opened position to a degreedetermined by the degree of inflation of said first actuator means;second actuable damper means movable between extreme opened and closedpositions to proportion air inflow through said second air inlet andhaving a front surface configured to block air flow through said secondair inlet when said second damper means is in its closed position, saidsecond damper means also including a rear surface; second bias means forcontinuously urging said second damper means towards its openedposition; a second actuator compartment located in said housing anddefined on at least one side by the rear surface of said second dampermeans; second inflatable and expansible actuator means disposed in saidsecond compartment for urging said second damper means towards itsopened position to a degree determined by the degree of inflation ofsaid second actuator means; cOntrol means for controllably inflating anddeflating said first and second actuator means with primary air, saidcontrol means including thermostatic valve means responsive to thetemperature in an environment being conditioned by said primary airstream for inflating one and deflating the other of said first andsecond actuator means with primary air; third actuable damper meansmovable to two extreme closed positions through an opened position toproportion air inflow through said third air inlet; linkage means forconnecting said first and second damper means to said third damper meanssuch that said third damper means is in its opened position and permitsmaximum air flow through said third air inlet when both of said firstand second damper means are closed.
 2. The system according to claim 1wherein said thermostatic valve means includes first and second valvesconnected to receive primary air through a common feeding port, saidvalves having respective outlet ports connected in parallel and feedingsaid first and second inflatable actuators, respectively, said valvesbeing arranged so that at least one of said outlet ports is open at anytime to feed said primary air to inflate its associated inflatableactuator and thereby close the corresponding one of said first andsecond damper means, said system further including bias means formaintaining said first and second damper means open when the associatedinflatable actuator is deflated, whereby contemporaneous opening of bothsaid first and second damper means is prevented.
 3. The system accordingto claim 2 wherein said first and second valves each includes a ventaperture for discharging primary air from the associated inflatableactuator when said each valve is closed, thereby causing the associatedone of said first and second damper means to open.
 4. The systemaccording to claim 3 wherein said thermostatic valve means is responsiveto a predetermined reference temperature in the environment beingconditioned for partially opening both said first and second valves,whereby said first and second actuators maintain said first and seconddamper means closed, the rate of air discharge from said vent aperturesbeing less than the rate of primary air flow through said common feedingport.
 5. The system according to claim 1 wherein said thermostatic valvemeans is responsive to the temperature in said conditioned environmentbeing less than a predetermined reference temperature for blockingprimary air inflow to said second inflatable actuator, whereby secondaryair flows through said second heat exchanger means, and wherein saidthermostatic valve means is responsive to the temperature in saidconditioned environment being greater than said predetermined referencetemperature for blocking primary air inflow to said first inflatableactuator whereby secondary air flows through said first heat exchangermeans.
 6. The system according to claim 1 further comprising means forbiasing said third actuable damper means in an open rest position, saidthird actuable damper means being rotatably mounted for rotation betweentwo closed positions which are symmetrically disposed relative to saidrest position.
 7. A local conditioning induction-type apparatus forconditioning systems with four pipes of secondary water, comprising:first and second heat exchangers, each arranged to have said secondarywater flowed therethrough via a respective pair of said four pipes; aby-pass flow section located between said first and second heatexchangers; a primary air flow section through which primary air isdirected to flow, and including an aspiration opening through whichsecondary air flow is aspirated by primary air flow; first and seconddamper means for controlling the temperature of said primary air flowfor controlling secondary air flow to said aspiration opening throughsaid first and second heat exchangers, respectively; third damper meansfor controlling the temperature of said primary air flow by controllingsecondary air flow to said aspiration opening through said by-pass flowsection; first and second expansion lung actuator means foralternatively opening and closing said first and second damper means,respectively; thermostatically controlled valve means for conductingprimary air to inflate said first and second expansion lung means inresponse to temperature conditions in an environment being conditionedby said primary air; connecting means linking said first and seconddamper means to said third damper means for controlling the position ofsaid third damper means in accordance with the positions of said firstand second damper means; and interlock means for preventing secondaryair from passing contemporarily through said first and second heatexchangers; wherein said third damper means is biased open at a restposition by a return spring and is rotatably mounted on a pivot aboutwhich it is rotatable between two closed positions symmetricallydisposed relative to said rest position; and wherein said connectingmeans comprises a sector gear rigidly mounted on said rotation pivot ofsaid third damper means, which sector gear meshes at the same time withtwo racks, each rack being connected witth one of said first and seconddamper means, said interlock means being provided for preventing any oneof said racks from moving when the other rack is operated by themovement of the associated damper means.
 8. An apparatus according toclaim 7, wherein said interlock means comprises two identical andsymmetric levers pivotedly mounted on the same rotation pivot of saidsector gear, each lever having a pawl adapted to be engaged by one ofsaid racks and a bracket means adapted to engage an end of the otherrack, both said levers being capable of rotating against the action ofcontrasting spring means as said pawl of one lever is engaged by a toothof the associated rack, thereby disengaging said bracket means from theother rack.
 9. An apparatus according to claim 7, wherein said racks areconnected with said first and second damper means by means of rodshaving adjustable length and cranks mounted on the rotation pivots ofthe same damper means.